1. Field of Invention
This invention relates to an improved spinning pot used for twisting and winding synthetic textile yarns. The "SPINNING POTS" are used for high speed spinning of yarn in textile industries in general and viscose yarn industries in particular.
2. Description of the Prior Art
As per known art, the spinning pots have been used for decades in large or small textile mills. The known pot forms a unitary construction or a cylindrical portion and the base plate therefor. It is mounted on a pot motor with its rotating axis vertical and driven at high speeds of rotation, typically 8000 rpm. Textile yarn filaments coming out of spinnerettes are directed through a funnel, to initially drop to the centre of the bottom surface of the pot where they are thrown outwards to the wall of the spinning pot by the centrifugal force due to high speed rotation of the pot. A periodic reciprocating motion, given to the funnel along the axis of the pot, winds the spun filament yarn into a helically wound `cake` which builds up uniformly along the internal wall of the spinning pot. The acidic liquid which is picked up by the yarn when it comes out of the coagulating bath is, to a large extent, removed from the `cake` by centrifugal action and thrown out through vent holes on the walls of the spinning pot.
The known spinning pot consists of a barrel having an integral base which is mounted on the shaft of a pot motor by means of a locating bush. There is also provided the usual air vent, acid vent and centre spot. The walls of the barrel of the pot have a plurality of stiffening reinforcements. The pot at the top has a lid, with a locking ring therefor. A funnel and funnel holder are fixed in the said lid for the admission of the yarn. The twisted yarn forms a cake on the inside of the pot.
All known pots now in use are essentially similar in shape and construction. The differences are generally limited to the type of central mounting bush, type of vent holes for excess acid or air, type of reinforcement to make the wall stiffer, type of closure at the top and its retention etc.
Thus, in order to make use of the known pots with the existing components involves the following sequence of steps in its operation:
(i) remove the entire spinning pot from the motor shaft; PA1 (ii) remove locking ring; PA1 (iii) remove lid; PA1 (iv) turn pot upside down; PA1 (v) lightly tap on a soft smooth surface and remove cake. PA1 (v) reduce the cost of raw materials used in the manufacture of the pots;
For starting the cycle of operation, the same sequence in reverse order has to be gone through.
When we consider that the cycle of operation is repeated by thousands of operators millions of times all over the world, saving in operator fatigue and production time is of great importance.
The drawbacks of the hitherto known spinning pots are:
The spinning pot is a highly stressed component which is subjected to cyclic loading of continuous duty;
All existing pots have the common drawback of high stress concentrations at the corner where the cylindrical wall meets the flat circular base;
Also the barrel portion of the vessel which is stressed to the highest level by the centrifugal force exerted by the wet cake, tends to expand into a large cylinder. But the flat circular bottom disc cannot expand equally. This leads to high flexural and shear stresses at the junction of the barrel and its flat circular base;
Furthermore, the base of the pot has large mass of costly acid resistant material which is discarded along with the condemned pots;
The bronze metal bush which is critically precision machined after fixing to the pot is of considerable cost and it is also discarded everytime a pot's life is over. Although the metal can be recovered, the recovery value is a minute fraction of the original cost;
The locating bore and face, being small in dimension have to be very accurate to have the pot run concentrically and in dynamic balance. Even small amount of wear in the bore tends to offset the concentricity and balance of the pot, leading to costly repair work of,
(i) rebushing the pot and PA2 (ii) re-balancing of the pot dynamically;
The existing pots typically weigh about 2 to 3 times the weight of the cake that is formed by spinning. As the operator takes out the entire pot to remove the cake for further processing, it means that the operator handles 2 to 3 times excess load twice for every cake for yarn produced. Although this looks trivial, it is of enormous magnitude, when one considers the total volume of production which runs into thousands of tons per day, affecting thousands of workers, who have to work in continuous exposure to acid fumes in the spinning section of the mill;
The existing pots also consume work energy for the following reasons:
(i) As the weight of the pot is high, the power for accelerating it to the top speed is high;
(ii) As the shape is such that both outer and inner contours cannot be given very smooth surfaces, the practice is to mould the inner surfaces to mirror finish and machine the outer contour by turning and polishing it by sanding;
(iii) As most of the energy consumed during the spinning is for overcoming the aerodynamic friction which is related to the smoothness of the surfaces and accuracy of concentric rotation, mirror smooth finish on all surfaces of the pot will result in substantial saving in energy consumption. As millions of spindles are in operation all over the world on continuous duty, the saving potential is enormous.